MD Settings: Allow the user to order the list of languages.

chrome/browser/resources/settings/languages_page/languages.js

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview 'settings-languages' provides convenient access to
  * Chrome's language and input method settings.
  *
  * Instances of this element have a 'languages' property, which reflects the
  * current language settings. The 'languages' property is read-only, meaning
@@ skipping 528 matching lines @@
           var inputMethods = this.languageInputMethods_.get(otherLanguageCode);
           return inputMethods && inputMethods.some(function(inputMethod) {
             return this.isComponentIme(inputMethod) &&
                 this.supportedInputMethodMap_.get(inputMethod.id).enabled;
           }, this);
         }, this);
     return otherInputMethodsEnabled;
   },
 
   /**
+   * Moves the language in the list of enabled languages by the given offset.
+   * @param {string} languageCode
+   * @param {number} offset Negative offset moves the language toward the front
+   *     of the list. A Positive one moves the language toward the back.
+   */
+  moveLanguage: function(languageCode, offset) {
+    if (!CrSettingsPrefs.isInitialized)
+      return;
+
+    var languageCodes =
+        this.getPref(preferredLanguagesPrefName).value.split(',');
+
+    var originalIndex = languageCodes.indexOf(languageCode);
+    var newIndex = originalIndex + offset;
+    if (originalIndex == -1 || newIndex < 0 || newIndex >= languageCodes.length)
+      return;
+
+    languageCodes.splice(originalIndex, 1);
+    languageCodes.splice(newIndex, 0, languageCode);
+    this.languageSettingsPrivate.setLanguageList(languageCodes);
+  },
+
+  /**
    * Enables translate for the given language by removing the translate
    * language from the blocked languages preference.
    * @param {string} languageCode
    */
   enableTranslateLanguage: function(languageCode) {
     languageCode = this.convertLanguageCodeForTranslate(languageCode);
     this.deletePrefListItem('translate_blocked_languages', languageCode);
   },
 
   /**
@@ skipping 190 matching lines @@
    * manually sending a change notification for our 'languages' property (since
    * it's the same object as the singleton's property, but isn't bound by
    * Polymer).
    * @private
    */
   singletonLanguagesChanged_: function(e) {
     // Forward the change notification to the host.
     this.fire(e.type, e.detail, {bubbles: false});
   },
 });